This invention relates to an image information detecting/processing method which is capable of detecting the pixel information on pixels of a whole frame on an original film such as a film negative, the frame being segmented into a large number of pixels, and automatically detecting the size and advancing direction of the frame by comparing the information with stored information of adjacent frames or of a reference frame so as to enable the use of a common operational expression for determining the exposure value.
It is necessary to photometrically measure the density of an original film such as a film negative sheet in order to determine the printing exposure value or the correction value thereof in a photographic printing system. In the prior art, the film negative is measured with respect to its LATD (Large Area Transmittance Density) by means of photosensors such as photodiodes provided near an optical path in the photographic printing system. The LATD method, however, is an image detection to photographically measure the film negative generally but is not a method to measure the image density of a film negative correctly or across the whole frame. The printing exposure value or correction value obtained by the LATD method therefore does not quite meet strict requirements. When the film negative is printed on a photographic paper, it is necessary to change exposure value or correction amount depending on the size, manufacturer or sensitivity of the film negative due to the difference in light diffusion particular to each film. These differences are conventionally observed and discriminated macroscopically and inputted manually from a keyboard or discriminated by a separate device, and signals thereof are read out from an information transmission medium. Such key manipulation or signal processing is not only cumbersome but susceptible to errors in input.
FIG. 1 shows a system which has been proposed by this applicant to solve such problems encounted in the prior art.
A film negative 2 is conveyed by a conveying mechanism 9 to a position on a film negative carrier 1. The negative film 2 is illuminated with the light from a light source 4 via a color compensation means 3 which comprises 3-primary color filters of yellow (Y), magenta (M) and cyan (C). The light transmitted through the film negative 2 is directed to reach a photographic paper 7 via a lens unit 5 and a black shutter 6. The photographic paper 7 is wound around a supply reel 7A and reeled on a take-up reel 7B in synchronism with the movement of the film negative 2. Photosensors 8 such as photodiodes are provided near the lens unit 5 of the film negative 2 in order to detect image density information of three primary colors. In accordance with the detection signals from such photosensors 8, picture printing is carried out. An image information detecting apparatus 10 comprising a two-dimensional image sensor 11 is positioned near the film negative 2 at a position inclined from an optical axis LS of the light source 4 and the film negative 2. A lens unit 12 is provided in front of the two-dimensional image sensor 11 to substantially focus the center area of the film negative 2. On the back of the image information detecting apparatus 10 is attached a substrate board 13 for mounting a processing circuit comprising integrated circuits and so on.
The two-dimensional image sensor 11 comprises, as shown in FIG. 2, an image pickup section 101 for optically picking up an image, a storage section 102 for storing charges transmitted from the image pickup section 101, and an output register 103 for outputting the charge stored in the storage section 102. By controlling driving signals 101S through 103S from a driving circuit, the image information in two-dimensions (area) in photoelectrically converted and outputted serially from the output register 103 in the form of an analog image signal PS. The circuit mounted on the substrate board 13 has, for example, a circuit structure shown in FIG. 3. The image sensor 11 is driven by driving signals 101S through 103S supplied from the driving circuit 20. The light illuminating the image pickup section 101 of the image sensor 11 is outputted from the output register 103 as a picture signal PS, sampled and held by a sample-and-hold circuit 21 at a predetermined sampling cycle. The sample value thereof is converted by an analog-to-digital (A/D) converter 22 into digital signals DS. The digital signals DS from the A/D converter 22 are inputted into a logarithmic converter 23 for logarithmic conversion, then converted to density signals DN, passed through a write-in control circuit 24 and finally written in a memory 25.
A reading speed signal RS from the driving circuit 20 is inputted into the write-in control circuit 24 in order to read out image information at a predetermined speed when the image sensor 11 is driven. The write-in control circuit 24 writes in the density signals DS at predetermined positions of a memory sequentially and correspondingly with the driving speed of the image sensor 11. In other words, the reading speed of the image sensor 11 is determined by the driving speed. The reading speed in turn determines the segmentation number of picture elements with respect to an image area. The memory 25 should therefore store the detected information in correspondence with the number of pixels, too.
When a picture is printed in a conventional manner in the above mentioned structure, the light transmitted through one frame of a film negative 2 which has been conveyed to and standing still at a printing position is detected by photosensors 8. Then, the filters in the color compensation means 3 are adjusted in response to the picture signals for each of the primary RGB colors and the black shutter 6 is opened to expose a photographic paper 7 with the determined exposure value.
An image information detecting apparatus 10 comprising a two-dimensional image sensor 11 of the area scanning type such as a CCD is mounted at a position near the film negative 2 at an inclined angle with respect to an optical axis LS to facilitate its mounting. The whole frame of the film negative 2 is segmented into a large number of arrayed pixels for detecting image information. In other words, when predetermined driving signals 101S through 103S are fed from the driving circuit 20 to the image sensor 11, the two-dimensional image sensor 11 is adapted to receive the light transmitted through the film negative 2 on the printing section via the lens unit 12. The two-dimensional image sensor 11 can therefore scan the whole surface of a frame of the film negative 2 along the scanning lines SL sequentially by segmenting the whole area into a large number of small arrayed pixels 2A as shown in FIG. 4A. After the whole area has been scanned, the output register 103 of the image sensor 11 outputs picture signals PS sequentially; then the picture signals PS are sampled and held by a sample-and-hold circuit 21 and the sampled values thereof are converted by an A/D converter 22 into digital signals DS. The digital signals DS from the A/D converter 22 are logarithmically converted by a logarithmic converter 23 to density signals DN. The density signals DN are controlled by a write-in control circuit 24 to be stored in a memory in the arrays corresponding to the pixels 2A shown in FIG. 4B and in terms of the density digital values of the film negative 2.
If the digital values for respective pixels of the film negative 2 or the density values for respective pixels with respect to the three primary colors are stored in the memory 25, it is possible to read out the digital values for any particular pixel of the film negative 2 from the memory 25. If the density values for respective three primary colors of R, G and B using mosaic filters (not shown) are stored as shown in FIG. 4B, it is possible to read out such values from the memory for processing (which will be described hereinafter) in order to determine the exposure or correction value for photographic printing in the same manner as in the prior art.
An example of the method for discriminating the size of film negative is described below.
An elongated film negative 2 is conveyed consecutively frame by frame by a conveying mechanism 9 to a position on a film negative carrier 1. As shown in FIG. 5, a rectangular upper guide 1B having a frame aperture 1A is engaged with a lower guide 1C positioned therebelow in order to hold the film negative 2 therebetween for printing the negative film 2 frame by frame. The size of the aperture 1A of the upper guide 1B is completely identical with the size of a frame of the film negative 2 so that the peripheral portion of the frame without an image or unexposed portion would not fall outside the area of the aperture 1A of the upper guide 1B. The area from which the two-dimensional image sensor 11 receives light is determined to correspond not only with one frame of the film negative 2 but also with a larger-sized film. The area includes the portion of the upper guide 1B where the light does not transmit. The image information of the area which the two-dimensional image sensor 11 detects is as shown in FIG. 6A in the case of a film negative carrier of 110 size while it becomes as shown in FIG. 6B in the case of a carrier of a 135 size. FIGS. 6A and 6B show examples of detected image information of the unexposed portion (the developed film portion where no image is pictured) wherein the portion VA encircled by broken lines at the center defines the aperture 1A or the area of a frame. Since the size of a frame corresponds to the size of a film negative 2, the size of an aperture 1A can be obtained by detecting the density "0" which means the transparent portion without image data read by the image sensor 11 and counting the area or the number of zero value pixels. This leads to the discrimination of the size of the film negative 2. In this case, since the optical axis of the image sensor 11 is directed toward the substantial center of the aperture 1A, the size of the film negative 2 can be discriminated by counting the number of pixels having the density "0" (or having the value close thereto) using either hardware or software and comparing the counted value with a predetermined value for each size.
As described above, the size of the film negative 2 is determined by measuring the area of the density "0" and corresponds to the number of pixels, which indicates the size of the aperture 1A of the film negative carrier 1. For example, as shown in FIG. 6A, if the number of pixels of the density "0" is "32" (which may be 30 to 34 for an allowance margin), the size is judged to be the 110 size, as shown in FIG. 6B; if the number is "160" (or 156 to 164 for an allowance margin), the size is judged to be the 135 size, and if the number is "196" to "204", the size is judged to be the 126 size. However, the method of size discrimination is not limited to the above method. The size information judged in the above manner is supplied to the photographic printing system so as to determine the exposure amount by the selection of the applicable formula or by the calculation using a formula related to the photographic printing process in correspondence with the particular film size.
In determining the exposure value, the transmittance of the light of the RGB color components over the whole area is controlled usually at a constant value so as to realize a print with balanced color and exposure. This is based on the empirical rule that the average reflectivity of transmittance of three colors obtained by integration of the whole scene, when an ordinary scene is photographed, is substantially constant. In other words, if a neutral object is photographed by a color film negative, the average LATD varies depending on the exposure amount, the quality of the light from a light source, the sensitivity of the RGB photo-sensitive layers of the color film, the mask used, etc., but those variations can be controlled by making the printing exposure value for R, G and B constant at the time of printing.
The variation in density of the three colors of a color film caused by the difference of color distribution of an object, on the other hand, cannot be controlled appropriately by the above mentioned method because the variation affects the area component ratio among the three colors. In the case where the composition in luminance is quite different from an ordinary distribution, e.g. one having an extremely large area of a high luminance or one with a large area of a low luminance, the LATD cannot be properly controlled by the method of merely controlling the printing exposure value using the average LATD because the variation in density on the film negative is caused by the area-wide variation of the density of the object. Similarly, if the main object of a scene has a shadowed portion or an extremely highlighted portion compared with the surrounding objects, the density cannot be corrected as there are involved conditions extremely different from those preset in the printer. In order to solve such problems in determining the printing exposure value, there have been proposed methods as disclosed in Japanese laid-open Pat. Nos. 23936/1977 and 28131/1979 and Japanese patent publication No. 2691/1981 which segment a frame of a film negative to obtain image information from each segmented portion, and determine the exposure value appropriate to the scene from all the information obtained from respective segments. If it is assumed that the average LATD of a frame is represented by Da, the maximum density of segmented frame by Dmax and the minimum density by Dmin, the exposure value X.sub.1 of a 135F size film can be determined by the following equation: EQU X.sub.1 =a1.multidot.Da+b1.multidot.Dmax+c1.multidot.Dmin+d1 (1)
The exposure amount X.sub.2 of a 110 size film can be determined by the following equation (2): EQU X.sub.2 =a2.multidot.Da+b2.multidot.DMAX+c2.multidot.Dmin+d2 (2)
If a correction formula Xs like the one shown below is made available for each film size, any film negative can be printed with a proper exposure value which has been properly corrected for the particular size. Coefficients K.sub.i and K.sub.j are determined separately by experiments for each size respectively. EQU Xs=K.sub.i +K.sub.j .multidot.X (3)
When an exposure value is determined or corrected with the information obtained from segments of a frame, there still remains a problem as to how to segment a frame. Another problem lies in that if segmentation method should vary depending on the size of the film, the calculation process becomes complicated. In order to avoid such an inconvenience, this invention enables one to determine the exposure value by means of a segmentation technique common to all sizes using a one-to-one correspondence between the number of segmented areas and the position thereof. More particularly, the above equations (1) and (2) are combined to obtain one common formula as follows: EQU X=a.multidot.D.sub.a +b.multidot.D.sub.max +c.multidot.D.sub.min +d (4)
Simultaneously, as shown in FIGS. 7A through 7E, the size of the pixels PX per se which are to be detected by the two-dimensional image sensor 10 is made constant for all the film sizes: a frame of a 135F size film as shown in FIG. 7A is divided into 16 groups, i.e. by four columns into elements C1A through C4A horizontally and into two-column, three-column, three column and two column elements R1A through R4A vertically, and the frame central data is obtained from the central area CP comprising 16 pixels. In a 135 size film as shown in FIG. 7B, a frame is divided into 16 groups by two horizontal columns into elements C1B through C4B and into two-column, three-column, three-column and two-column elements vertically R1B through R4B and the frame central data is obtained from the central area CPB comprising 16 pixels. In a 126 size film as shown in FIG. 7C, a frame is divided into 16 groups by 3 horizontal columns to the elements C1C through C4C and two-column, three-column, three-column and two-column elements vertically R1C through R4C and the frame central data is obtained from the central area CPC comprising 16 pixels. Similarly, a frame of 110 size is divided into 16 groups each of which comprises two horizontal columns and one vertical column (C1D through C4D horizontally and R1D through R4D vertically) and the central area CPD comprises four pixels. The disk size film of FIG. 7E is divided into 16 groups by segmenting a frame into two-column, one-column, one-column, and two-column elements horizontally C1E through C4E and by one vertical column R1E through R4E and the central area CPE comprises four pixels. In this manner, all the frames of respective film sizes are divided into 16 groups E1 through E16 of segments and all the central areas CPA through CPE are defined to include the center of the frame to obtain image information. It is therefore not necessary to change the reading-out area of the image sensor for various film sizes. With only one common equation, a frame can be processed for any film size. One segment area may comprise plural elements; however, it is possible to obtain image information of each segmented area simply by calculating a mean value of each element data. Since the frames of respective film sizes comprise area groups E1 through E16 and the central areas CPi (i=A through E), and since the average information of respective area groups E1 through E16 and CPi can be easily calculated from the data of component elements, the exposure value can be obtained by using the above formula (4) and the obtained exposure value can be corrected properly by the above formula (3), even if the size of each film negative conveyed to the printing section varies.
As described above, in the conventional size detection by means of an image sensor, a film negative carrier is detected without mounting any film negative frame or an unimaged frame and is detected before the start of printing operation. The method has a drawback in that it can not detect the size of a frame for confirmation if the film negative carrier is taken out and mounted again to change the size of a film frame during a continuous printing operation.
FIG. 8 shows the photographic printing system wherein a film negative 2 is mounted and advanced in either one of the two directions; i.e. the direction (referred to as "lateral transportation" hereinafter) parallel to the advancing direction of a photographic paper 7 or the direction (referred to as "longitudinal transportation" hereinafter) perpendicular thereto. A film negative other than the size 126 which is square in shape is transported in the system in either one of the aforementioned two transportation directions in order to limit the type of the photographic paper 7 as well as to enhance the efficiency in printing. In this type of printing system where the transportation direction as well as the size of the input frames are frequently switched, however, the above mentioned image information detecting method can not quite accomodate itself to the changes in transporting direction or changes of film negative carriers and often causes errors which waste a large amount of photographic paper.